Waxprecipitation is an important problem in the oil and gas industry so that itmay cause plugging of the process equipment and traortation pipelines during oiltraortation, production and refining. Therefore, an accurate thermodynamicmodel for prediction of the wax appearance temperature (WAT) at especially highpressures can be helpful to deal with this problem. In this work, an improvedthermodynamic model based on multi solid (MS) model of wax precipitation whichis coupled with the Chain form of the Statistical Associating Fluid Theory (PC-SAFT) equationof state (EOS) has been developed to correlate the WAT values. Also the MSmodel of wax precipitation has been coupled with the Peng Robinson (PR) EOS inorder to be compared with the proposed model. After plotting bubble curve, solid-liquidequilibria (SLE) calculations were employed for the pressures above the bubblecurve, and vapor-liquid-solid equilibria (VLSE) calculations were utilizedbelow the bubble curve in P-T diagram. In the proposed model, the crude oil has beenconsidered as a mixture of the paraffinic, naphthenic and aromatic fractionsand the plus fraction has been characterized using the threeparameters gamma probability function theory, in order to improve thecharacterization of the previous models based on two parameters gammaprobability function theory. The results of the model were compared in highand low conditions of the bubble curve with the available experimental data inthe sources as well as with experimental data measured at the Oil IndustryResearch Institute for 9 samples of Iranian oil. The results of thecorrelated values show that the proposed model based on PC-SAFT EOS with thecorrelated parameters can predict the WAT values better than the MS model withPR EOS with %AAD below %1 at a wide range of pressures. The improvement in the proposed model is about %0.5 relative to the PR equation.